The insert of the present invention relates to the metalworking industry and the geometric design of hard wear resistant "throw away" types of the cutting inserts.
Hard wear resistant materials, such as cemented hard metal carbides, have revolutionized the metal-working industry since their introduction back in about 1927. For a look at the tremendous impact that hard wear resistant cutting inserts, especially cemented hard metal carbides, have had upon the industry, reference should be made to FIG. 6 on Page 9 of Cemented Carbides by Dr. Paul Schwarzhopf and Dr. Richard Keiffer, published by The Macmillan Company in 1960.
FIG. 6 referenced therein shows that between 1900 and 1927 the cutting speed for sixty minutes of tool life increased only from 80 ft./minute to 120 ft./minute. With the introduction of the cemented carbides over the then used high speed tool steel, the cutting speed for sixty minutes of tool life then increased dramatically from the 120 ft./minute to up around 800 to 1,000 ft./minute by the 1960 publication date of the book.
Today, further improvements in the materials forming the cutting tools have added significantly to the cutting tool life such that the sixty minute tool life referred to in the reference has been increased at least an order of magnitude greater than shown in the referenced graph.
The advent of the tremendously increased speeds did not, however, come without its problems. Before the increased speeds became possible, the only concern was the removal of metal material from the workpiece. The question of how the cut metal came away from the workpiece was of no main concern to anyone as the thin continuous metal flowing from the cutting tool at those low speeds could easily be guided by the machine operator into a waste bin or other suitable container.
For this reason, with most of the machining prior to 1927, the metal removed from the workpiece came off as a continuous strip of material and simple guidance and observance by a careful operator was all that was required to maintain safe removal and disposition of the removed metal.
However, from about 1927 and on, with the significantly increased cutting speeds, and the also increasing strength of the cutting inserts, the increasing feeds and speeds were producing a very dangerous working condition for the machine operator.
First, the increased speed of continuous metal removal meant that the metal was coming off the workpiece at a faster rate than the machine operator might react to and, further, a thicker, stronger chip was being produced by the increased feed rates so that, even if the operator could possibly react to the snaking chip, he might not be strong enough to bend the snaking chip to his will. The fact that the snaking chip was also red hot, in addition to the above problems, now made the situation very dangerous and solutions to the safety problems had to be achieved.
The solution to the chip problem from the time the problem came into being until the present invention has resided in one form or another of mechanically bending the snaking chip as it comes from the workpiece so as to break it into small individual chips that fall harmlessly to the floor before endangering the operator and, also, do not interfere with the cutting edge of the cutting tool and the workpiece surface.
"Chip breakers" then came into existence and were recognized as necessary to the metalworking industry. Chip breakers took many forms but, essentially, operated on the principal that the chip should first flow away from the cutting edge of the cutting tool before it could be acted upon. Once away from the workpiece, it was then recognized as necessary to place a mechanical obstruction in its free flow path to mechanically force the chip to bend away from its free flow path and thereby break into small chips and fall harmlessly into a suitable container.
Cutting inserts, heretofore, have been made and used in conjunction with chip breaker or chip control regions in the form of rises formed thereon spaced inwardly from the cutting edge. Other inserts utilized a separate chip breaker in the form of a super-structure which was clamped against the insert. Using either form of chip controller involves extra expense and inconvenience, either in the molding of the insert or the insert set-up configuration.
In addition to the extra expense and inconvenience of the chip breakers, there is, further, the fact that the forced metal deflection as the chip flows into the rising chip breaker element requires greater machine horsepower consumption than if the chip were to flow freely across the surface of the cutting tool.
As the prior art of chip breakers has progressed, there has been produced a large number of chip breaker configurations and cutting insert geometries that provide higher speeds and feeds for certain materials but are within limited ranges for each application or use. The chips that are produced in one given set of working parameters (such as feed, speed and type of metal workpiece) usually are not so satisfactory when the parameters change out of their narrow and limited range of usefulness.
In the present age of numerical controlled machines, the need for efficient metal removal with effective chip control is absolutely essential. What is also essential is a cutting insert capable of achieving the efficiency and chip control over wider ranges of parameters of speeds, feeds and type of metal workpiece. Tool planners for the numerical controlled machines would then be able to buy more standard cutting inserts, thus, reducing overall tooling costs and less set-up time would be required for changeover of cutting set-ups from one machining job to another.
It has been found by tests and experimentation that an insert according to the present invention can be formed so as to eliminate the need for a rising chip breaker, or chip control, surface on the insert, or for an extra chip control member, at least for a large class of work.
With the foregoing in mind, a primary object of the present invention is the provision of a cutting insert having improved cutting characteristics and which is relatively simple to mold.
Another object of the present invention is the provision of a cutting insert in which the land area is exposed for any finishing operations it might be desired to carry out thereon.
Another object is the provision of an insert in which complex chip control configurations are eliminated thereby making it simpler to mold the insert and requiring less material in the insert.
Another object of the present invention is the provision of a broader range of chip control than is obtainable with previous insert designs.
Another object of the present invention is the provision of a cutting insert which reduces the machine power consumption required for cutting and is less expensive and gives a much broader range of chip control than previously known.